We have a hostel near a university in Amsterdam that always fills up on the evening before soccer matches. Data shows us that when our hostel is fully booked, the number of last-minute cancellations has a mean of 8 and standard deviation of 4. The average room rate is $50. When our hostel is overbooked, the policy is to find a room in a nearby hostel and to pay for the room for the customer-we prefer not to loose our customers. This usually costs us $70-because we have to book rooms on late notice which are expensive. How many rooms should our hostel overbook?